The present invention relates generally to an improved heat exchange apparatus such as an evaporative closed circuit cooling tower, evaporative fluid cooler or evaporative condenser. More specifically, the present invention relates to an evaporative fluid cooler or evaporative condenser having indirect evaporative fluid heat exchange sections arranged in such manner that an evaporative liquid, usually water, is distributed across the indirect heat exchange section. When compared to other similarly sized indirect, evaporative heat exchange products, the indirect heat exchange section of present invention is capable of achieving greater heat transfer capability per unit size and lower operating cost due to a use of less water flow rate as evaporative liquid.
In accordance with the present invention, a generally uniform temperature liquid is distributed over the outside surface of an indirect heat exchange section, which is comprised of a series of individual, enclosed circuits tier conducting a fluid stream to be heated or cooled. When used as a closed circuit cooling tower or evaporative condenser, heat is indirectly transferred from the fluid stream to the surrounding film of evaporative liquid. Heat retained by the evaporative liquid is directly transferred to an air stream passing through the indirect evaporative heat exchange section. The evaporative liquid draining from the indirect heat exchange section, is then collected in a sump and then pumped upwardly for redistribution across the indirect evaporative heat exchange section.
Depending upon the specific application, the fluid stream can be used to either liberate or absorb heat to or from the air stream, making the value of the heat exchanged to the air stream either positive or negative.
The present invention is concerned with an indirect heat exchange apparatus and method which achieves maximization of the heat exchange efficiencies of the indirect heat exchange section.
In an indirect evaporative heat exchanger, three fluid streams are involved; an air stream, an evaporative liquid stream, and an enclosed fluid stream. The enclosed fluid stream first exchanges sensible heat with the evaporative liquid through indirect heat transfer, since it does not directly contact the evaporative liquid, and then the evaporative liquid and the air stream evaporatively exchange heat and mass when they directly contact each other.
The majority of closed circuit cooling towers evaporative fluid coolers and evaporative condensers are stand alone indirect evaporative heat exchangers.
The present invention represents a unique improvement over the prior art by offering the most efficient way to operate such heat exchangers.